1. Field of the Invention
The present invention relates to an oil pump structure for supplying lubricating oil to an engine.
2. Description of Background Art
Japanese Patent No. 2688926 shows an oil pump structure in which lubricating oil in an oil pan is delivered from a scavenging pump to an oil tank, and the lubricating oil in the oil tank is supplied to respective portions of an engine by a feed pump. A relief valve is provided between respective delivery paths of the feed pump and the scavenging pump, and when delivery pressure on the side of the feed pump becomes higher than a predetermined value, the relief valve is opened and a lubricating oil escapes to the side of the delivery path of the scavenging pump.
Further, Japanese Examined Patent Publication No. 88820/1995 shows an oil pump structure in which a relief valve chamber extends in a direction orthogonal to a rotor rotational shaft and is provided integrally with a cover of an oil pump. In this structure, a relief path is formed in a circular arc shape at a face of bonding the cover and a main body portion of the oil pump enabling the lubricating oil escaping from the relief valve chamber to return to an intake side of the oil pump.
As described in Japanese Patent No. 2688926, when the lubricating oil that reaches a predetermined high pressure and escapes from the relief valve to the oil tank on the low pressure side, it is necessary to circulate the lubricating oil by taking in the lubricating oil by the feed pump from the oil tank. Thus, pump efficiency is lowered.
In Japanese Examined Patent Publication No. 88820/1995, the relief valve chamber is formed integrally with the cover of the oil pump, resulting in a cover and a total pump structure that is large and relatively heavy in weight. Further in this structure, the relief path is comparatively long, and is formed in a direction orthogonal to the axis of the rotor rotational shaft and the axis of the crankshaft. Thus, when the oil pump, as described in the reference, is attached to the inside of the crankcase, the relief valve chamber projects into an inner space of the crankcase, and a comparatively large space is needed for its layout in order to avoid interference with other parts.
Hence, it is an object of the present invention to provide an oil pump that is efficient to operate, small in size, light in weight, and also affords excellent space efficiency.
In order to improve upon the designs shown in prior art, the present invention provides an oil pump structure of an engine characterized in that an engine is attached with an oil pump for taking in a lubricating oil from an oil pan and pressurizing the lubricating oil to supply to respective portions of the engine by bonding the oil pump to a crankcase. The present invention also provides a relief valve for adjusting a delivery pressure that is contained in a relief valve chamber formed over a face of bonding the crankcase and the oil pump in parallel with a rotor rotational shaft of the oil pump, and, in addition provides a relief path from the relief valve that is formed by directly connecting the relief valve chamber and an intake chamber of the oil pump contiguous thereto.
According to the present invention, the relief valve chamber is formed to cross over the crankcase and the oil pump, the relief valve is contained in parallel with the rotor rotational shaft, and therefore, the relief valve chamber can be formed by utilizing the inside of wall thickness of the crankcase. As compared to conventional structures, the present invention affords excellent space efficiency. Further, by bonding the oil pump to the crankcase, the relief valve can be interposed conveniently in a small space between the crankcase and the oil pump. Further, the relief valve chamber is directly connected to the intake side of the oil pump contiguous thereto, resulting in a relief path that is relatively short, and a total oil pump structure that is small in size, light in weight, and that has excellent pumping efficiency.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.